<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        div {
            margin: 50px;
            width: 10em;
            height: 6em;
            background: #fb3;

            /*box-shadow: 2px 3px 4px rgba(0, 0, 0, .5)*/
            /*单侧投影*/
            /*box-shadow: 0 5px 4px -4px black;*/

            /*邻边投影*/
            /*box-shadow: 3px 3px 6px -3px black;*/

            box-shadow: 5px 0 5px -5px black,
                -5px 0 5px -5px black;
        }
    </style>
</head>
<body>
    <div>
    </div>
</body>
</html>